Morpholine Preparation from Diethanolamine

The synthesis of morpholine from diethanolamine.

Morpholine Procedure: 62.5 g of diethanolamine is added to a round bottom flask with a thermocouple and air condenser. Concentrated hydrochloric acid is added until a pH of 1 is reached (~50-60 mL of HCl). The diethanolamine hydrochloride solution is heated, driving off the water until an internal temperature of 200-210 °C is reached, this temperature is maintained for 15 hours. After 15 hours, the mixture is allowed to cool to 160 °C before being poured out of the flask into a dish to prevent solidification inside the flask. The thick morpholine hydrochloride paste is scraped into a blender and mixed with 50 g of calcium oxide. The resulting paste is transferred to a round bottom flask and subjected to a strong and dry flame distillation. A dark, crude, and very wet morpholine is recovered. This is dried by stirring over 20 g of potassium hydroxide for about 30 min to an hour. The mixture is decanted or filtered if necessary into a separatory funnel and the upper morpholine layer is recovered. The morpholine is then refluxed over a small amount (~1 g) of sodium metal for one hour before rearranging the apparatus for fractional distillation. The morpholine product is collected in the range of 126-129 °C (My product was distilled over at 128-132 °C, bad thermocouple probably). A yield between 35-50% should be expected.

4-Tosylmorpholine Procedure: 0.26 g Tosyl chloride is dissolved in 2.5 mL acetone, to this is dropwise added a solution of 0.27 g morpholine in 0.5 mL acetone, this is then stirred for 3 minutes. 10 mL of water is then added followed by 0.5 mL of 10% sodium hydroxide solution, this is then stirred for 5 minutes before being filtered, washed with water, and air dried. The recovered yield was 78%, melting at 146.8 °C (Literature 147-148 °C).

The wiki page for morpholine lists the dehydration of diethanolamine with sulfuric acid as a method of synthesis but after some digging in the literature, I saw that it typically only gives single-digit yields with the methods that use standard laboratory glassware.

Literature Paper: https://pubs.acs.org/doi/pdf/10.1021/...
https://doi.org/10.1021/ja01302a504

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